Fiberboard is commonly used in the building construction industry for panels and tiles, such as ceiling tiles. Generally, fiberboard includes primary components held together with a binder. Primary components typically include mineral fiber, such as mineral wool, cellulosic fiber and a filler component. Starch is a binder favored by the industry.
Fiberboard is often installed in bathrooms, laundry rooms, and kitchens where it is exposed to high humidity. Fiberboard panels are occasionally soaked with water from pipe or roof leaks. Humid and/or wet conditions generally cause conventional fiberboard to deteriorate.
Exposure to moisture weakens the starch binder of mineral fiberboard. Fiberboard also absorbs moisture which increases its weight. Water-laden or weakened fiberboard can sag and/or break. This is a particular hazard when the fiberboard is used for ceiling tiles. Additionally, fiberboard panels can buckle from lateral expansion due to water absorption.
Various attempts to address moisture-related problems with fiberboard have been made. Attempted solutions include coating the fiberboard with a moisture barrier layer and laminating the mineral fiberboard with a stiffening layer to form a composite structure. These methods add to the difficulty and cost of manufacturing the product.
Another attempt to improve the moisture resistance of fiberboard is to replace the starch with a water-resistant binder. U.S. Pat. No. 4,861,822 discloses an alkali-swellable polymer, latex binder for cast ceiling tiles. U.S. Pat. No. 4,587,278 discloses moisture-resistant, mineral fiberboard compositions including 4-20 weight percent of an acrylate/acrylonitrile/styrene copolymer binder.
U.S. Pat. No. 5,134,179 teaches strengthening acoustical ceiling tile of mineral fiberboard by using a newsprint fiber component coated with a latex binder. These methods require special materials which add significantly to the product cost.
It is desired to provide a moisture resistant, starch-bound fiberboard which can be produced without significantly changing existing manufacturing methods and/or adding to costs.